1. Field of the Invention
The present invention relates to a multiplex transmission system which processes control specification information relevant to control specifications of loads by multiplexing via a multiplex transmission system, and which is connected to load control units capable of controlling the loads respectively connected thereto. More particularly, the present invention relates to a vehicle multiplex transmission system which is connected to load control units capable of controlling the electric power fed to loads, that is, electrical equipment such as lamps or an air conditioner, aboard the vehicle. The present invention further relates to a resetting method and a resetting apparatus for use with the multiplex transmission system.
2. Related art
FIG. 15 shows an example of a conventional multiplex transmission system of the above described type.
Specifically, a multiplex transmission system 5 is made up of one single master load control unit 1, at least one slave load (two slave load control units 2 and 3 shown in FIG. 15), and a multiplex transmission network 4 connecting them together.
The master load control unit 1 and the slave load control units 2, 3 are respectively provided with nonvolatile storage sections 1a, 2a, and 3a for holding control specification information.
The nonvolatile storage sections 1a, 2a, and 3a of the master load control unit 1 and the slave load control units 2, 3 hold control specification information which are control specifications of loads 2b, 2c, 3b, and 3c in a multiplexed manner through the multiplex transmission network 4.
Control status information or control specification information, which are held in the nonvolatile storage sections 1a, 2a, and 3a in a multiplexed manner, are updated by connecting, e.g., an external write terminal to the master load control unit 1, and by writing the control status information or control specification information to be updated into the nonvolatile storage section 1a of the master load control unit 1 from the external write terminal.
The control specification information, that is, the control specifications of the loads 2b, 2c, 3b, and 3c, represent the types of loads 2b, 2c, 3b, and 3c (e.g., electrical equipment aboard the vehicle such as lamps and an air conditioner), and control methods (e.g., the accurate control of a flashing cycle of the lamps, illuminance of the lamps and lightening actions of a lamp synchronized with door openings, and the control of supply of electrical power such as ON/OFF operations of the air conditioner).
The slave load control unit 2 selectively controls either the load (L1)2b or the load (L2)2c by switching between a selective switch (S1)6a and a selective switch (S2)6b, as required.
Similarly, the slave load control unit 3 selectively controls either the load (L3)3b or the load (L4)3c by switching between a selective switch (S1)6a or a selective switch (S2)6b, as required.
That is, the respective slave load control units 2 and 3, in accordance with the load control information that has been processed in a multiplexed manner, are allowed to selectively control either of the loads (either L1 or L2) respectively connected to the unit 2, and either of the loads (either L3 or L4) respectively connected to the unit 3.
In the multiplex transmission system 5 in normal operation, for example, the master load control unit 1 enters a transmission mode, and the control specification information or the control status information is transmitted during a predetermined period of time (i.e., in a period of "a" sec. in FIG. 16). Each slave load control unit enters a receiving mode during only a predetermined period of time (i.e., in a period of "a+.alpha." sec. in FIG. 16) by use of a built-in timer. It then receives the control specification information or the control status information from the master load control unit, and the thus received information is held in the respective nonvolatile storage sections 2a and 3a.
Subsequently, the slave load control unit 2 enters a transmission mode and transmits the control specification information or the control status information during a predetermined period of time (i.e., in a period of "b" sec. in FIG. 16). At this moment, the master load control unit 1 and the slave load control unit 3 enter a receiving mode during only a predetermined period of time (i.e., in a period of "b+.alpha." sec. in FIG. 16) by use of their respective built-in timers. Then, they receive the control specification information or the control status information from the slave load control unit 2. The thus received information is held in the respective nonvolatile storage sections 1a and 3a.
Similarly, the slave load control unit 3 enters a transmission mode and sends the control specification information or the control status information during a predetermined period of time (i.e., in a period of "c" sec. in FIG. 16). The master load control unit 1 and the slave load control unit 2 enter a receiving mode during only a predetermined period of time (i.e., in a period of "c+.alpha." sec. in FIG. 16) using their respective built-in timers. Then, they receive the control specification information or the control status information from the slave load control unit 3. The thus received information is held in the respective nonvolatile storage sections 2a and 1a.
According to a resetting method and a resetting apparatus used in such a conventional multiplex transmission system 5, the master load control unit 1 enters the transmission mode first to start initial-mode communication at the time of a restoring operation (e.g., a resetting operation) for restoring the system in an abnormal condition to a normal condition. As a result, the control specification information held in the master load control unit 1 is forcibly multiplexed with respect to other load control units (i.e., the slave load control units 2 and 3), and the thus multiplexed information is stored in the respective nonvolatile storage sections 2a and 3a. On the basis of the control specification information or the control status information forcibly multiplexed by the initial-mode communication executed when the system is restored from an abnormal condition to a normal condition (e.g., at the time of a resetting operation), the slave load control unit 2 controls the loads 2b and 2c connected thereto. Similarly, the slave load control unit 3 controls the loads 3b and 3c connected thereto on the basis of the control specification information or the control status information forcibly multiplexed by the initial-mode communication executed when the system is restored from an abnormal condition to a normal condition (e.g., at the time of a resetting operation).
The abnormality arising in the multiplex transmission system signifies anomalous communication in a multiplex transmission network or faulty operations of the load control units which could be due to an anomaly in the power supply.
Problems to be Solved by the Invention
However, in the above-mentioned conventional multiplex transmission system 5, if any of the respective pieces of load control information respectively held in the storage part 1a of the master load control means 1, the storage part 2a of the slave load control unit 2 and the storage part 3a of the slave load control unit 3 is multiplex processed under such a condition that it is updated in error due to noise or the like, or if the multiplex processing is executed under such a condition that the load control information is transmitted in error due to noise or the like, there is a fear that the multiplex transmission system 5 will fail to operate normally. This raises a problem as to the reliability of the multiplex transmission system 5.
Also, in such abnormal operating conditions of the multiplex transmission system, there is a fear that the required pieces of load control information (such as the kinds of the loads, the load control methods and the like) respectively consisting of the control contents of the loads can be updated in error due to noise or the like. This would thereby cause the wrong selection and control of the loads that are the objects to be controlled. This also raises a problem as to the reliability of the multiplexing transmission system 5.
Further, the conventional system fails to provide a means which can, when the load control information of the master load control means 1 is updated, not only can urge the forced transfer of the updated load information to the respective slave load control units 2 and 3 but also allows the thus transferred load control information to be held by the respective storage parts 2a and 3a of the slave load control units 2 and 3. Thus, the conventional procedure for updating the load control information is apt to be complicated, which raises a problem that the updating of the load control information cannot be transmitted to the slave load control unit with accuracy.
Further, if the control status information or the control specification information held in the nonvolatile storage sections 1a, 2a, and 3a is updated in such a conventional multiplex transmission system 5, an external write terminal, or the like, is connected to the master load control unit 1. The control status information or the control specification information to be updated is written into the master load control unit 1 from the external write terminal. This makes it difficult to quickly, accurately, and easily initialize the multiplex transmission system. Further, it is difficult to design a multiplex transmission system using new control specification information located at a place distant from the multiplex transmission system. Hence, it is difficult to quickly, accurately, and easily update the conventional multiplex transmission system.
Further, according to the resetting method and the resetting apparatus used in the conventional multiplex transmission system 5, the master load control unit 1 enters the transmission mode first to start the initial-mode communication when the system is restored from an abnormal condition to a normal condition (e.g., at the time of a resetting operation). Then, the control specification information held in the master load control unit 1 is forcibly multiplexed with respect to other load control units (i.e., the slave load control units 2 and 3). As a result, the load control unit in normal operation is also forcibly subjected to the initial-mode communication carried out to restore the system from an abnormal condition to a normal condition (e.g., to reset the system).
As described above, the load control unit being normally operating is also forcibly subjected to the initial-mode communication which uses the control specification information or the control status information of the master load control unit 1. As a result of this, normal load control and multiplexing operations being executed by the normal load control unit is interrupted.
In other words, the control and multiplexing operations of the normally operating load are interrupted when the system is restored from an abnormal condition to a normal condition (e.g., at the time of a resetting operation), and the load control and multiplexing operations for the initial-mode communication are executed instead. It is difficult to resume the interrupted load control and multiplexing operations which require a high degree of reliability and accuracy.